The main ingredients used in the gas evolution model for the KB are summarized in Table REF  and the main timescales in Table REF . The main ideas go as follows: 1) CO is released from planetesimals in the KB. 2) CO is quickly pushed outwards with a velocity \(\gtrsim \)  3 au/yr due to collisions with high-velocity (\(\sim \)  400 km/s) protons from the solar wind (and a small fraction of the CO gets ionized and dissociated during these collisions and due to impinging photons from the Sun and the interstellar medium). 3) Most CO gets pushed beyond the heliopause [1]}, [2]} before it has time to dissociate or ionize. 4) CO finally turns into C+O and C gets ionized due to photons from the interstellar medium, while O gets ionized due to collisions with protons from the local cloud of the interstellar medium that is colliding with our Solar System. 5) Then the ionized atoms follow the interstellar magnetic field lines and get ejected further into the local interstellar medium.
More details about each step of the model are given in the following sections.
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